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356 A77ierican Seashelh
Genus Botula Morch 1853
Subgenus Adula H. and A. Adams 1857
Botula falcata Gould Falcate Date Mussel
Coos Bay, Oregon, to Lower California.
Plate 29k
2 to 4 inches in length, very elongate, slightly curved. Beaks rounded
and about one-eighth the length from the anterior end; a strongly marked
angle occurs from the beaks to the base of the posterior extremity; numerous
vertical, wavy ribs over all the shell. Color a shiny chestnut-brown. Com-
mon.
Botula californiensis Philippi Californian Date Mussel
Plate 29h
I to 1^4 inches in length, elongate, curved and smooth, except for a
velvety, hair-like covering over the posterior end. Shiny, chocolate-brown
in color. Moderately common.
Genus Lioberus Dall 1898
Lioberus castaneus Say Say's Chestnut Mussel
Both sides of Florida and the West Indies.
% inch in length, oval-elongate, well-inflated and thin-shelled. Exterior
chestnut- to dark-brown, the anterior half glossy, the posterior half dull
and commonly with a fine grayish matting of periostracum. Interior bluish
white and with an irregular surface. Hinge simple with a slight swelling or
pad under the beaks. Moderately common in shallow water.
Botula fusca Gmelin from North Carolina to southeast Florida (rare)
and the West Indies (common) is similar, but distinguished by its longer,
hooked or arcuate shape, by the thick, concentric ridges on the outside, by
the more anteriorly placed beaks, and by the tiny, vertical threads on the
hinge just posterior to the ligament. Attached in clusters to wood and
rocks.
Genus Lithophaga Roding 1798
Lithophaga nigra Orbigny Black Date Mussel
Southeast Florida and the West Indies.
Plate 2 8in
I to 2 inches in length, elongate and cylindrical. Black-brown outside
and an iridescent bluish white inside. Anterior lower third of each valve